The present invention relates to a technique for processing a measurement signal.
Measurement devices, such as sensors, bridge circuits, or the like, have a disadvantage that they often superpose a first offset signal on the measurement signal of interest to the user. This offset signal is due to the mechanical sensitivity of the measurement device, inaccuracies in the manufacturing technique of the measurement devices, and/or the electronics. The magnitude of this offset signal is often unknown to the user and varies in time.
Some measurement devices, such as Hall sensors or Wheatstone bridges can be driven in such a way that the offset signal is alternately added to and subtracted from the measurement signal. Therefore, the offset signal is superposed on the measurement signal as an AC signal, preferably a square-wave signal. Driving the sensors or bridge circuits in this way is often referred to as "chopping". The frequency that the offset signal changes sign is called the "chopper frequency".
The chopper frequency is typically selected to have a much higher value than the maximum frequency of the measurement signal, so the high frequency offset signal can be separated from the measurement signal by a low-pass filter to obtain an offset-free measurement signal.
A disadvantage of this technique is the complication associated with the circuitry involved in filtering the signal, and the fact that filtering usually creates a new offset. Therefore, there is a need for a system and method for obtaining the measurement signal without the need for filtering.